(1) Field of the Invention
The present invention is directed to the fabrication of unitary structures, such as missile radomes, from fiber reinforced plastic material. More particularly, the present invention is directed to a unitary structure and method of manufacture thereof wherein at least one layer is comprised of woven or non-woven long filaments of a high strength material combined with a fluorocarbon polymer.
(2) Description of the Prior Art
The present invention has particular utility in the field of radomes.
Ceramic radomes are typically used for missiles intended to operate at speeds of Mach 4 or higher. These ceramic radomes have been found to be at best marginal in performance due to fragility, susceptibility to thermal shock, high thermal conductivity and high rates of rain impact damage. A definite need exists for a workable alternative to ceramic radomes.
Radomes of polymeric composite materials and methods of manufacture thereof are disclosed in U.S. Pat. No. 4,364,884 and co-pending application Ser. Nos. 263,191; 339,839 now U.S. Pat. No. 4,451,833 and 342,057, all of which are assigned to the assignee of the present invention and the entire disclosures of which are incorporated herein by reference.
U.S. Pat. No. 4,364,884, discloses a novel radome and method of making a radome comprised of a fiber reinforced plastic material wherein the fibers are to a high degree randomly oriented perpendicular to the axis of the radome.
In co-pending application Ser. No. 263,191, a novel radome structure comprised of a fiber reinforced plastic material is disclosed wherein the fibers are to a high degree randomly oriented parallel to the nearest or inner surface of the radome. This arrangement greatly improves longitudinal strength over the radome disclosed in U.S. Pat. No. 4,364,884, although perhaps at some sacrifice in resistance to rain erosion and ablation.
Both of the inventions disclosed by the above-identified applications provide various structural properties that are useful for differing applications.
Co-pending application Ser. No. 263,191 also discloses the use of a layer or liner, comprised of filaments or a honeycomb of high strength material saturated with an epoxy or polyimide resin. The liner is bonded to the interior of and forms a support for the polymeric fiber-reinforced composite material which forms the radome. This type of liner is easily produced, since epoxy and polyimide resins can be applied in liquid form to the filaments and then shaped before curing.
While the radomes of U.S. Pat. No. 4,364,884 and co-pending application Ser. Nos. 263,191; 339,839 and 342,057 are suitable for many applications, there are other applications and requirements (especially for radomes for noses of very high velocity missiles, such as on the order of 1300 meters/sec. (2900 miles/hour)) where there is a need for a radome having combined properties of high modulus, good electrical properties at microwave frequencies, good resistance to ablation and high strength to an extent not heretofore available.